1. Technical Field
The disclosure relates to a method for controlling a powder compacting apparatus, and relates also to a compacting apparatus.
2. Description of Related Art
One of the methods for compacting powder under pressure is a float compacting method. The float compacting method is carried out by using a powder compacting apparatus that mainly includes a die having a hollow, a floating lower punch that slides in the hollow, an upper punch that is also slidable in the hollow, and various actuators that respectively drive the floating lower punch and the upper punch.
Powder is charged into a cavity defined by the die, the floating lower punch, and the upper punch. Then, the powder is pressurized by pushing down the upper punch by using an actuator, such as a hydraulic cylinder or an air cylinder. At this time, the powder is pressurized while the floating lower punch is slid by an actuator such that a prescribed pressurizing force (floating load) acts on the powder. There is also a powder compacting apparatus in which a stationary lower punch that does not slide is disposed around a floating lower punch, and a cavity is defined by the stationary lower punch, the floating lower punch, a die, and an upper punch.
There is also a powder compacting apparatus configured such that, in addition to a floating lower punch and an upper punch, a die can also be slid by an actuator. In the thus configured powder compacting apparatus, the upper punch and the floating lower punch pressurize powder while descending at prescribed respective rates (speeds). At this time, for example, while the upper punch is descending at a speed of 10 and the floating lower punch is descending at a speed of 7, the die is also descending, for example, at a speed of 8. With this configuration, when the powder is gradually compacted from the vicinity of the upper punch to produce a green compact, it is possible to inhibit the generation of a density distribution in which the density of the green compact decreases with increasing proximity to the upper punch (i.e., a density distribution in which the density of the green compact becomes lower as the distance to the upper punch decreases in the green compact).
In the float compacting method, when the powder is pressurized due to the descending of the upper punch, the operation of the floating lower punch is controlled such that a floating load applied to the powder by the floating lower punch becomes a setting value, and the floating lower punch reaches a stopper that defines a pressurization stop position while maintaining the floating load.
After completion of the pressurization, the floating load is reduced when the green compact obtained by compacting the powder is removed from the die.